From c8d5cb240588d5eb4582c4397d5f58ebbf8229e1 Mon Sep 17 00:00:00 2001
From: Erik Arvstedt <erik.arvstedt@gmail.com>
Date: Wed, 1 Jun 2022 21:35:50 +0200
Subject: [PATCH] examples: improve Flakes-based VM

- Show login message
- Poweroff on shell exit
- Move to top of examples/README
---
 examples/README.md              | 22 ++++++++++++++++------
 examples/qemu-vm/minimal-vm.nix | 16 +++++++++++++++-
 2 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/examples/README.md b/examples/README.md
index bc71860..64a54df 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -1,8 +1,22 @@
-Examples
----
+## Examples
 
 The easiest way to try out nix-bitcoin is to use one of the provided examples.
 
+### Flakes-based quick start
+
+If you use a Flakes-enabled version of Nix, run the following command to start a minimal
+nix-bitcoin QEMU VM:
+```bash
+nix run github:fort-nix/nix-bitcoin/release
+```
+The VM (defined in [flake.nix](../flake.nix)) runs in the terminal and has `bitcoind`
+and `clightning` installed.\
+It leaves no traces (outside of `/nix/store`) on the host system.
+
+
+### More examples
+
+Clone this repo and enter the examples shell:
 ```bash
 git clone https://github.com/fort-nix/nix-bitcoin
 cd nix-bitcoin/examples/
@@ -79,7 +93,3 @@ The commands in `shell.nix` allow you to locally run the node in a VM or contain
 
 Flakes make it easy to include `nix-bitcoin` in an existing NixOS config.
 The [flakes example](./flakes/flake.nix) shows how to use `nix-bitcoin` as an input to a system flake.
-
-Run `nix run` or `nix run .#vm` from the nix-bitcoin root directory to start an example
-nix-bitcoin node VM.
-This command is defined by the nix-bitcoin flake (in [flake.nix](../flake.nix)).
diff --git a/examples/qemu-vm/minimal-vm.nix b/examples/qemu-vm/minimal-vm.nix
index 041a310..eb89eb6 100644
--- a/examples/qemu-vm/minimal-vm.nix
+++ b/examples/qemu-vm/minimal-vm.nix
@@ -13,7 +13,7 @@ rec {
 
   vm = (import "${nixpkgs}/nixos" {
     inherit system;
-    configuration = {
+    configuration = { lib, ... }: {
       imports = [
         nix-bitcoin.nixosModules.default
         "${nix-bitcoin}/modules/presets/secure-node.nix"
@@ -28,6 +28,20 @@ rec {
       virtualisation.graphics = false;
       services.getty.autologinUser = "root";
       nix.nixPath = [ "nixpkgs=${nixpkgs}" ];
+
+      services.getty.helpLine = lib.mkAfter ''
+
+        Welcome to nix-bitcoin!
+        To explore running services, try the following commands:
+        - nodeinfo
+        - systemctl status bitcoind
+        - systemctl status clightning
+      '';
+
+      # Power off VM when the user exits the shell
+      systemd.services."serial-getty@".preStop = ''
+        echo o >/proc/sysrq-trigger
+      '';
     };
   }).vm;